I have a DPMS 308B with an 18in 308 chambered barrel and am considering switching to a 7.62x51 chambered barrel with a low profile upper. The reason for this thought is to be able to use surplus 7.62x51 ammo which DPMS frowns on in their 308 barrels.

Basically, the only differences are 7.62x51 is has a .005" longer chamber spec, and the 308 has a 62,000 psi cartridge spec and 7.62x51 has a 50,000 psi cartridge spec. I Honestly wouldn't worry about changing your barrel unless your just looking for a reason to rebarrel your rifle.

In a DPMS rifle it is safe to shoot both 7.62x51mm and .308 from the 7.62x51mm chamber.

We do not recommend 7.62x51mm in a .308 chamber though due to extraction issues and increased wear.

Oh, and the pressure thing, it is 62000 PSI for 308, and 50000 CUP for 7.62x51. They are measured differently and are not equal units. There is correlation, but they are not equal. Correlating PSI and CUP

Originally Posted By Lmccrock:
Oh, and the pressure thing, it is 62000 PSI for 308, and 50000 CUP for 7.62x51. They are measured differently and are not equal units. There is correlation, but they are not equal. Correlating PSI and CUP

The TM 43-0001-27TM 43-0001-27 has the 7.62 at 50/52K PSI not CUP. Your assumption is wrong